Itching is an unpleasant, complex skin sensation which evokes the reflex response of scratching or the desire to scratch. The act of scratching arises as a protective reflex, and leads to the formation of a skin lesion.
Itching is a frequent disorder, although it is generally considered a benign symptom, and can have adverse effects on the patient's well-being and quality of life, and even become disabling when it is severe (1). As it was long considered to be a sub-type of pain, no attention was paid to its neurobiological aspects. Recent studies have demonstrated that itching has a different pathophysiology from pain, and does not have a parallel trend to the underlying disorder. It involves a series of dermatological conditions, but can also be a marker for a systemic disorder. Itching has been classified as follows: cutaneous, neuropathic, neurogenic and psychogenic.
Cutaneous itching is caused by inflammation of the skin, neuropathic itching originates from a nerve lesion, and neurogenic itching originates at central level with no evidence of a neurone disease, as in the case of cholestasis. Finally, psychogenic itching is present in states of delirium (2). Itching is in any event a subjective sensation, and an exhaustive nosographic classification has not yet been developed.
Localised itching is usually caused by dermatosis, with well-defined identifiability and clinical characteristics, such as urticaria, lichen planus, scabies and pediculosis, psoriasis, atopic or contact dermatitis, seborrhoeic dermatitis and lichen simplex.
As regards the treatment of itching, it is generally recommended that the skin should be kept cool and well hydrated, because the intensity of itching increases with body temperature and skin dryness. Topical products based on capsaicin are used for localised itching, and TENS and CFS (cutaneous field stimulation) are also used in resistant cases. Antihistamines are not usually very effective unless the itching is mainly mediated by histamine, as in the case of urticaria (4). In fact, recent studies have demonstrated that histamine is not the main mediator of itching, which is why the efficacy of antihistamines is low (5).
These medicaments present adverse effects on the heart and liver (to a lesser degree and with lower sedative effects in the case of second-generation antihistamines). They must therefore be prescribed cautiously to patients with liver failure or at risk of cardiac arrhythmia.
Topical and systemic corticosteroids are not anti-itching drugs, and are only effective in alleviating part of the itching resulting from inflammatory alterations of the skin. These drugs also have serious side effects, mainly associated with their long-term use or abrupt termination of the treatment: they can cause damage to the gastric mucosa, accumulation of fat on the face and neck, muscle thinning, osteoporosis, hyperglycaemia, reduction in resistance to infection, increased wound-healing time, etc.
Oral doxepin, a tricyclic antidepressant, is a potent anti-itching agent, but must be prescribed with great care, especially for patients with cardiovascular and liver disease, initially at low doses, and must not be abruptly terminated, nor prescribed together with other antidepressants, antibiotics or antifungals. Other antidepressants, such as selective serotonin reuptake inhibitors (SSRIs), and antiepileptics, such as gabapentin, are also used (4). In these cases, the adverse effects are headache, nausea, vertigo, drowsiness, irritability, tremors, etc.
In this scenario, it is unsurprising that anti-itching treatments must be considered “immature”, and the choice of therapeutic options still limited.
There is consequently a strongly felt need for an itching treatment which is minimally invasive, devoid of adverse effects, perfectly tolerated by the largest possible number of people and, at the same time, effective and active in a short time, these latter characteristics being essential to ensure compliance by patients, in view of the discomfort caused by a symptom like itching.
A therapeutic option with these characteristics would be particularly indicated in all cases of localised short-term itching, conditions in which aggressive treatments not lacking in side effects and contraindications would not be very advantageous, with a high risk/benefit ratio.
An anti-itching composition consisting of a combination of resveratrol, glycyrrhizic or glycyrrhetinic acid and artemisinin obtained from Artemisia annua (“ginghaosu”) is described in Chinese patent CN101829130.
French patent FR 2 873 025 describes a patch based on resveratrol.
Chinese patent application CN 10189130 describes topical formulations of resveratrol for the treatment of skin diseases.
However, the combination of resveratrol with eugenol or extracts containing it has not been described to date.